Medical imaging has been an expanding field for several decades. With increasing diagnostic tools, increasing population, more widespread access to medical treatment, and the desirability of sharing information between doctors and professionals, medical imaging is very likely to continue growing at a rapid rate. To address this continued growth, and the subsequent inconveniences of paper and other fixed forms of medical image storage, the medical community has increasingly turned to digital forms of image storage.
Picture Archiving and Communications Systems (PACS) are a common example of a digital image system. These systems connect elements such as imaging modalities, storage databases or areas, clients that use the medical image data, and data processing devices to create a network of imaging technology. Such systems then provide easier remote diagnosis and data access, sharing of information between health-care professionals, and ultimately a better health-care system.
Currently, large volume Computed Tomography (CT), Magnetic Resonance (MR) and X-Ray Angiography (XA) DICOM studies acquire a large number of image data files that must be transferred within and between local PACS networks. A typical image dataset can easily contain over 2000 slices that translates into a similar number of image data files.
Enterprise Picture Archiving and Communication Systems (PACS) deployments, such as those found in a hospital, provide a centralized means of searching, retrieving and storing images using the Digital Imaging and Communications in Medicine (DICOM) protocol. Key to the concept of a PACS is the archiving component. Using the underlying principle of time-based or rules-based storage, acquired DICOM objects such as images are kept on long-term media for retrieval at a later time, through a centralized location. Images may be stored on a variety of media, including but not limited to Magneto-Optical Disc (MOD), Digital Linear Tape (DLT), Compact Disc (CD) or Digital Versatile Disc (DVD).
Accordingly, medical images may have been transmitted from multiple locations within a hospital. Often, the originating source of the image, while referenced in the DICOM metadata, may not have been the last known sender of the medical image. This downstream mechanism presents a dilemma in multiple-node PACS deployments when it is desired to delete an image study from a particular PACS.
It may be desirable to delete an image study for reasons of storage space conservation. Another reason is the practical difficulties associated with maintaining duplicates of an image study. For example, the DICOM standard requires that each medical image should have a unique identifier (known as the sop_instance_uid). Also, some PACS implementations will refuse to accept duplicate medical images. As such, it may be necessary to delete the medical image study in order to enable a retransmission. If an image study transmission has resulted in data corruption due to external influences (media, network, etc), then a manual deletion may become necessary.
At the same time, image data retention and integrity is highly desirable and generally speaking, an imaging study should not be deleted if it is not available on another PACS within the network. However, the final archive destination may not be the initial PACS accepting the image data. There is currently no adequate means of verifying that a particular imaging study is safe to delete (i.e., stored elsewhere). Thus, it is desirable to provide a means of assurance for study, series, image and object persistence and availability in a multiple-node PACS environment.